The claimed invention is directed toward modified HIV-1 gp41 C-terminal heptad repeat fusion inhibitors. In particular, peptide derivatives of C-34 were prepared (e.g., FB006M) and modified with 3-maleimidoproionic acid (MPA), which allows rapid and irreversible conjugation to serum albumin at a 1:1 molar ratio. These polypeptides have an extended half-life in vivo and display potent antiviral activity against HIV-1.